Why is my car so bad at coasting

[wdb]

Originally Posted by MetroMPG

(For our U.S. friends: 6 km = 4 mi.)

Short trips like this with lots of stops are not at all ideal for getting good fuel economy, even with neutral coasting where practical. The car never really warms up, and vehicles don't get their best economy until they're completely warmed up (entire drivetrain, not just engine coolant).

Absolutely true. I'm utterly jealous of your short commute - mine is more like 120km! I have a ScanGauge, and the mileage I get rolling out of my neighborhood and onto the more open secondary roads is abysmal. Once on those roads, and as the car gets warmed up, the MPG's go up in a hurry.

In other words, as odd as it may sound, you would probably see better MPG's by driving further. While I definitely encourage you to do what you can to improve the number, If I were you I'd stop feeling bad about your commuting MPG's and start taking pride in your phenomenal commuting GPP's (gallons per person).

[jayliu1984]

Originally Posted by XYZ

Assuming it is not in gear, no wheel should be difficult to turn when the wheel is off the ground. There could be several possible causes. Examine it and find where the problem is.

I have a short youtube clip showing how "hard" it is to turn my front wheel.

The car is jacked up one side and is in neutrual.

As you can see, the wheel is stiff, but I checked the brakes, they are not hot at all when I drove around.

And to the person above, yeah I like the short commutes, it only takes me 10 minutes to get to work. However, I still can't stop thinking how much money I would have saved if I have gotten a different car. I had no idea this accord uses this much fuel. The EPA rating is 21MPG city, and I am only getting 18.6, while being laughed at by my coworkers the way I drive (too granny).

I just like rule out any possible causes for bad fuel comsumption. If I can be SURE that this car is all good and this IS how much gas Honda Accord drinks, it helps me to make decision if I want to sell the car when the lease is up or keep it. There is nothing I would complaint about the car except the fuel comsuption.

3

[PaleMelanesian]

That's not right at all! You should be able to turn it with 1 or 2 fingers and have it continue to rotate 1/2 turn or more before stopping.

edit: both front wheels off the ground spins much easier than just one.

[jayliu1984]

Originally Posted by PaleMelanesian

That's not right at all! You should be able to turn it with 1 or 2 fingers and have it continue to rotate 1/2 turn or more before stopping.

Are you sure? I raise this concern among my friends and some of them say it is normal because I am turning the trans as well.

Please, I need more people to confirm this before I bring it in to the dealer. I just don't wanna make a fool of myself.

So the engine is OFF, gear is in N, and hand brake was OFF, it is an automatic I4, one side is jacked, the other front wheel is off the ground.

[MetroMPG]

I don't think the video is a smoking gun. Looks normal to me.

A rear wheel (with drum brakes) will spin freely with little effort, after a one finger push, and keep spinning. I've never seen a front wheel spin freely.

If you had a dragging brake (e.g. siezed caliper) you'd be able to smell the brakes after a long drive, or you'd be able to feel significantly more heat by touching the wheel near the hub after a drive (compared to a rear wheel).

I thought we already determined that the coasting "problem" is fixed by shifting to neutral.

[jayliu1984]

Originally Posted by MetroMPG

I don't think the video is a smoking gun. Looks normal to me.

A rear wheel (with drum brakes) will spin freely with little effort, after a one finger push, and keep spinning. I've never seen a front wheel spin freely.

If you had a dragging brake (e.g. siezed caliper) you'd be able to smell the brakes after a long drive, or you'd be able to feel significantly more heat by touching the wheel near the hub after a drive (compared to a rear wheel).

I thought we already determined that the coasting "problem" is fixed by shifting to neutral.

Well, the car does coast further in N, BUT, what if there is a problem with the wheel?

let's say you have some jam in the wheel so you can only coast 90% of what normal car can coast, that means 20% overall inefficiency (when half the time you are accelerating?). And there is no way to tell. It is not like a jammed brake where it is obvious.

I guess the only way to tell is to find another accord and try spining it again.

[PaleMelanesian]

Ah, I know what I was thinking of! If you have both front wheels off the ground it should spin a lot more freely. The opposite wheel will spin in reverse due to the differential.

(just watch out for pinching your fingers between the wheel spokes and the brake caliper. )

[user removed]

Get a cheap laser thermometer, or borrow one. Check each wheel after a drive. If any wheel is significantly hotter than the others, look at that wheel first. If the fronts are close to the same temp and the rears also, you probably don't have any serious problems, unless you can hear a bearing noise. Alignment might be worth checking.
Frozen e-brake cable or sticking calipers could create a hot wheel-wheels.

Bottom line is you are not coasting unless the transmission is in neutral.


regards
Mech

[roosterk0031]

Since N coasting is good, I think you should take a HWY drive and get some HWY numbers to see if the car is running properly.

And don't accelerate like grandpa, brisk acceleration with an auto to get it into top gear (or atleast highest gear for the PSL) as quick as possible without going over say 3000 rpm is better, if going between lights, accelerate brisk to just fast enough to neutral coast to next light. N coasting at 30 mph will net you +100 mpg.

If the speed limit is high enough you need to get the torque convertor locked up, but with my older auto's they won't lock up for 2-3 miles at below freezing temps ever at 55 mph.

Make shift engine heater, put a flood light under your oil pan and get a timer to turn it on a few hours before you leave in the morning, nothing to remember to unplug.

[user removed]

In almost any automatic the best rate of accelerating is a fast as possible while not delaying upshifts. I have driven my Fiesta from dead cold with the MPG meter (factory and slightly optomistic) reset. In 4 miles I can get it to over 40 MPG even in winter with temperatures just above freezing. Coasting in neutral is the key to getting decent numbers. Next is timing any traffic lights to try to catch them green, to minimize your cold engine idling which is a huge hit for mileage.

I get an extra hit when pulling out of my driveway which is a ten foot elevation increase in the first 70 feet. By the time I am at 3/10 mile at the end of my neighborhood I can usually get to 35-30 MPG. In that .3 mile I have coasted more than half the distance. Even with a cold engine, coasting still gives very high mileage, but it must be in neutral.

regards
Mech